Intro to FEA for 3D printing

Finite Element Analysis (FEA) is a tool commonly used by engineers to solve solid mechanics problems. With FEA, engineers can predict how a part will behave under a given set of loads and constraints dictated by how the part is used. FEA is often used to determine the displacement profile of the part, as well as to know whether the part will fail. Engineers use this information to validate their designs.

A key input to an FEA is data on the materials used to build the part. Depending on the material properties, the stress and displacement profiles will look different, and therefore the failure thresholds. Traditional manufacturing methods have well-defined material datasheets that can be used as input for an FEA, but 3D printing poses three key new challenges linked to the layering process:

(1) Imperfect bonding between layers causes anisotropy of the part’s properties, meaning that properties along the vertical axis are different from properties along the horizontal axes.

(2) The wide range of printing parameters combinations (infill %, layer height, infill pattern) lead to very different outcomes.

(3) In the case of Fused Deposition Modeling (FDM), the presence of an outer surface (see definitionhere) makes the properties of the part dependent on its geometry.

3D Matter started addressing these challenges by developingOptiMatter, a model that forecasts the properties of printed materials depending on the printing parameters used. However, OptiMatter does not address the geometrical side of the equation. Now, 3D Matter has developed a proprietary methodology to conduct Static Linear Finite Element Analysis on 3D printed parts, with a focus on FDM parts. Thanks to this new tool, we can accurately predict if a printed part will yield or not.

This articles shows the results we obtain on a case study example and provides empirical validation of the accuracy of our model.

3D Matter provides data on 3D printed materials throughOptiMatter, our cloud-based optimization software. There are many insights on materials that can be derived from this data, as illustrated by the studies we publish on this website, which are all based on the data fromOptiMatter.

However, we are aware that most users do not have the time or the expertise to process this raw data, and that’s why we are currently building tools to help users make the most ofOptiMatter.

Our latest development is the addition of a visualization tool that enables you to upload an STL file to obtain data on the object you want to print. Data points such as material cost, building time and weight can now be quantified for your specific object. Furthermore, you can select specific cross-sections of your object and get mechanical data for these cross-sections, such as the max load it can sustain.

We have prepared a tutorial to get you started with the new tool, and we hope it helps you make the most ofOptiMatter!

Intro

Choosing the right type of material to print a given object is becoming increasingly difficult as the 3D printing market sees the emergence of radically new materials. In FDM 3D printing, PLA and ABS have historically been the two main polymers (= type of plastic) used, but their initial dominance was mostly fortuitous. So there should not be any major road blocks for other polymers to play a key role in the future of FDM. We are now seeing new products become more popular, both pure polymers and composites. In this study, we focus on the main pure polymers that exist in the market today: PLA, ABS, PET, Nylon, TPU (Flexible) and PC. We sum up the key differences between their properties in snapshot profiles, so that users can make a quick decision about the best polymer to use for their application.

3D Matter is releasing the first version of their online optimization softwareOptiMatter. It is a forecasting model that will help users choose the best materials and the best printing parameters for their applications. It provides a wide range of data on materials, technologies and parameters and calculates the best printing configuration based on the user’s requirements.

You can try the free version with basic PLA and PET, or get access to the full version with over 30 products already available, and many more coming soon! Use Promo code: I3DP3DM16 and get 30% off for the first 3 months if you sign up before the end of May 2016!

The outer surface of a print

If you are a frequent FDM 3D printer user you have probably already tried modifying the parameters called “number of shells / perimeters”, “top solid layers” or “bottom solid layers” in your slicer. These parameters represent “the outer surface” of your object. Currently, different slicers call each of these parameters different names. In the table below, we show a few examples of the different terminology used by various slicers to reference the outer surface and its components, as well as how 3D Matter refers to them for the purposes of this article:

Flexible filaments arrived on the market a couple of years ago and have really broadened the range of objects that can be made with personal 3D printers. While flexibility is a new dimension to the material selection that users can now tap into, this dimension has not been well investigated.

There are many suppliers of flexible materials, and this diverse product selection is also associated with a wide range of filament flexibility levels, mechanical performance, visual quality and processability. Also, there is currently little understanding of how to use a given filament to get the right flexibility for prints, in particular by adjusting the infill %.

This study compares a set of six flexible filaments along various criteria to provide users with a point of comparison among current suppliers. It also gives insight into how to use flexible filaments to reach the right level of flexibility, and the key parameters to adjust when printing this type of material.

3D Matter just hired a new employee and his name is Testman! Testman is a very efficient worker: he appraises geometrical accuracy and visual aesthetics in a single print. His versatility makes him adapted to any material that needs to be assessed, providing us with a consistent test for the years to come. Who is he? Well, he is our new quality testing 3D file!

A key challenge to testing a material’s visual quality is the lack of consistent test that would assess most of the criteria that constitutes what “good” quality is. Texture and details are important if you are printing a small statue, but geometrical accuracy is more important if you are printing a door handle. So in order to provide an overall assessment of material’s quality, there are a number of tests that need to be conducted.

In February 2015, 3D Matter conducted a study on infill %, layer height, and infill pattern. We wanted to continue this initial effort by studying another set of very important FDM 3D printing parameters: filament color, printing speed, extrusion temperature and ageing. These are parameters that 3D printer users have frequently singled out as making a difference on the outcome of prints. So the goal of this study is to distinguish the factors that have a large influence on the printed parts from those that have limited influence. This helps users optimize their prints by focusing on the important parameters.

In the main body of this study, we provide a detailed description of the influence these four parameters have on mechanical performance: max stress, elongation at break, and rigidity (Young Modulus). We also evaluate the influence of the parameters on the visual quality of printed objects.

PLA and ABS are the two most used plastics in the personal 3D printing market, constituting about 75% of the current market[1], due in large part to their good printability. So it is no surprise that many of filament companies want to keep the same base chemistry but improve the properties of these materials. In our first study on filament providers, we tested a few modified filaments and found that while the visual quality of these filaments was better, their mechanical performance was actually reduced by the modifications.[2]

How about PLA and ABS filaments that have been modified to improve mechanical performance or processability? What is the extent of the improvement compared to the base chemistries? What is the impact of these improvements on visual quality?

In this study we first lay out the pros and cons of basic PLA and basic ABS, and then we use our testing procedure to show how improved filaments compare in terms of performance, quality and process.

Improving the mechanical performance of a printed part often comes at the expense of printing speed, affordability and quality. In this study we quantify the impact of different parameters on performance, and we try to help users choose the optimal settings by clearly laying out the trade-offs faced by the user. We provide the settings we would pick depending on the application requirements.

The key parameters we look into are infill %, layer height and infill pattern. In the main body of this study, we provide a detailed description of the influence these parameters have on max stress, elongation at break, rigidity (Young Modulus) and yield stress.